The synthesis of two parental BN anthracenes, 1 and 2, was developed, and their electronic structure and reactivity behavior were characterized in direct comparison with all-carbon anthracene. Gas-phase UV-photoelecton spectroscopy studies revealed the following HOMO energy trend: anthracene, -7.4 eV; BN anthracene 1, -7.7 eV; bis-BN anthracene 2, -8.0 eV. The λmax of the lower energy band in the UV-vis absorption spectrum is as follows: anthracene, 356 nm; BN anthracene 1, 359 nm; bis-BN anthracene 2, 357 nm. Thus, although the HOMO is stabilized with increasing BN incorporation, the HOMO-LUMO band gap remains unchanged across the anthracene series. The emission λmax values for the three investigated anthracene compounds are at 403 nm. The pKa values of the N-H proton for BN anthracene 1 and bis-BN anthracene 2 were determined to be approximately 26. BN anthracenes 1 and 2 do not undergo heat- or light-induced cycloaddition reactions or Friedel-Crafts acylations. Electrophilic bromination of BN anthracene 1 with Br2, however, occurs regioselectively at the 9-position. The reactivity behavior and regioselectivity of bromination of BN anthracenes are consistent with the electronic structure of these compounds; i.e., (1) the lower HOMO energy levels for BN anthracenes stabilize the molecules against cycloaddition and Friedel-Crafts reactions, and (2) the HOMO orbital coefficients are consistent with the observed bromination regioselectivity. Overall, this work demonstrates that BN/CC isosterism can be used as a molecular design strategy to stabilize the HOMO of acene-type structures while the optical band gap is maintained.

In the crude oil, the other fractions such as hydrocarbons could be adsorbed and/or occluded inside asphaltene structures. In this work, the deuterated compound n-C 20 D 42 has been used to simulate the adsorption/occlusion characteristics of asphaltene in toluene solution. Based on the highly polydispersed structures of asphaltenes, the experimental results indicate that the adsorbed hydrocarbons could be exchanged with the outside bulk phase, whereas the occluded ones inside the core of asphaltenes could not be exchanged. These results suggest that substantial microporous units exist inside asphaltene structures, and these structural units are suitable to adsorb and occlude the other fractions in the crude oil. The carbon number of the occluded hydrocarbons could be up to C 40 , and the weight could be more than 0.5%, based on the initial asphaltene weight. The adsorption should occur at the periphery of asphaltene aggregates (the loosely packed ones), and then they are liable to be exchanged with the outside bulk phase. If the asphaltene molecule is large enough, the occlusion could occur at the asphaltene molecular level. However, this type of occlusion perhaps just occurs inside asphaltene aggregates (the close aggregating ones); if this is the case, this type of asphaltene aggregate should be considered to be the stable unit in toluene solution, and then the occluded hydrocarbons could not be exchanged with the bulk phase. Regarding the adsorption/occlusion properties of asphaltenes, the aforementioned results should be valid, even extrapolated into the crude oil reservoir system.

We present a comprehensive electronic structure analysis of structurally simple BN heterocycles using a combined UV-photoelectron spectroscopy (UV-PES) / computational chemistry approach. Gas-phase He I photoelectron spectra of 1,2-dihydro-1,2-azaborine 1, N-Me-1,2-BN-toluene 2, and N-Me-1,3-BN-toluene 3 have been recorded, assessed by density functional theory calculations, and compared with their corresponding carbonaceous analogues benzene and toluene. The first ionization energies of these BN heterocycles are in the order N-Me-1,3-BN-toluene 3 (8.0 eV) < N-Me-1,2-BN-toluene 2 (8.45 eV) < 1,2-dihydro-1,2-azaborine 1 (8.6 eV) < toluene (8.83 eV) < benzene (9.25 eV). The computationally determined molecular dipole moments are in the order 3 (4.577 Debye) > 2 (2.209 Debye) > 1 (2.154 Debye) > toluene (0.349 Debye) > benzene (0 Debye) and are consistent with experimental observations. The λmax in the UV-Vis absorption spectra are in the order 3 (297 nm) > 2 (278 nm) > 1 (269 nm) > toluene (262 nm) > benzene (255 nm). We also establish that the measured anodic peak potentials and electrophilic aromatic substitution (EAS) reactivity of BN heterocycles 1–3 are consistent with the electronic structure description determined by the combined UV-PES/computational chemistry approach.